diff --git a/rust/prop_grid_rs/src/scores_file.rs b/rust/prop_grid_rs/src/scores_file.rs
index aa6c5b86..f3394fa5 100644
--- a/rust/prop_grid_rs/src/scores_file.rs
+++ b/rust/prop_grid_rs/src/scores_file.rs
@@ -236,9 +236,10 @@ mod hrdps_tests {
         // HRDPS bbox lat_start=49, lon_start=-141
         assert!((decoded.lat_min - 49.0).abs() < 1e-6);
         assert!((decoded.lon_min - (-141.0)).abs() < 1e-6);
-        // 89 lat × 713 lon cells per the Canadian bbox.
-        assert_eq!(decoded.n_rows, 89);
-        assert_eq!(decoded.n_cols, 713);
+        // HRDPS uses the coarser 0.5° step (see grid::HRDPS_STEP), so
+        // the bbox produces 23 lat × 179 lon cells.
+        assert_eq!(decoded.n_rows, 23);
+        assert_eq!(decoded.n_cols, 179);
     }
 }